Four-button trackball



FIG. 1 is a left side plan view of a four button trackball showing the new design.

FIG. 2 is a right side plan view thereof.

FIG. 3 is a front side plan view thereof.

FIG. 4 is a back side plan view thereof; and,

FIG. 5 is a top plan view thereof.

The broken line drawing of a portion of a cord in FIGS. 1, 2, 3 and 5 is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a four button trackball, as shown and described. 